Method for determining calibration for measuring transit time

ABSTRACT

The invention relates to calibrating a device or a system for signal-transit-time measurement or signal-transit-time-measurement-based distance measurement on the basis of at least one phase measurement. A method for calibrating at least one system for carrying out a signal-transit-time measurement where the system is designed, in cooperation with a first object, to carry out a distance measurement on the basis of a phase measurement, at least one first distance measurement to the first object being carried out by means of phase measurement, particularly by phase shifting and/or modifying a phase shift by the frequency, and at least one signal-transit-time measurement or a second distance measurement carried out on the basis of at least one signal-transit-time measurement to or via the first object. The system is calibrated on the basis of at least one signal-transit-time measurement by means of the at least one first phase measurement.

TECHNICAL FIELD

The invention relates to calibrating an apparatus or a system for signaltime-of-flight measurement or signal time-of-flight-measurement-baseddistance measurement on the basis of at least one phase measurement.

BACKGROUND ART

Determining a distance between two objects by means of radio signalsover times-of-flight of the radio signal is known. Using phase shifts toascertain the distance is also known.

SUMMARY OF THE PRESENT INVENTION

It is desirable to provide a simple and reliable approach forcalibration.

The inventor has found, surprisingly, that apparatuses for phase-baseddistance measurement, particularly currently commonly-used Bluetoothapparatuses and Bluetooth chips, have much less fluctuation within aseries than those for signal time-of-flight-based distance measurement.This applies particularly in relation to the phase-based distancemeasurement, and the signal time-of-flight-based distance measurement,or the signal time-of-flight measurement, of a single apparatus or of asingle chip. In particular, currently commonly-used Bluetoothapparatuses and Bluetooth chips have much less fluctuation within aseries for phase-based distance measurement or phase measurement thanfor signal time-of-flight-based distance measurement or signaltime-of-flight measurement. It is thus possible to calibrate the signalToF-based distance measurement without much effort on the basis of aphase-based distance measurement. Thus, in relation to the phase-baseddistance measurement an apparatus or a pair of apparatuses of a seriesor model range can be calibrated exemplarily and this calibration can beused for the phase measurements of all apparatuses of the series.Thereby, all apparatuses in the series can be calibrated easily andautomatically in relation to the signal time-of-flight measurement anddistance measurements based thereon. This can be done for the firstdistance measurement of the respective apparatus or between a pair ofthe apparatuses. This is even possible for a pair made up of differentmodel ranges or series, provided each one has a series-specific- and/ormodel-range-specific calibration with regard to the phase-based distancemeasurement.

In particular, accuracies of signal time-of-flight-based distancemeasurements in the 2.4 GHz band are typically around one meter for ameasurement on the basis of an amplitude rise or an amplitude modulationwith usual components, wherein without calibration, further inaccuracyin the order of 1.5 meters applies. The advantage of the present methodbecomes yet more apparent when a frequency modulation is used for thetime-of-flight-based distance measurement, since here an elimination ofan error contribution of around 20 m can be expected by the calibration.After a calibration according to the invention, an accuracy in the orderof one meter can be expected.

The problem is solved by a method for calibrating at least one systemfor carrying out a signal time-of-flight measurement and/or signaltime-of-flight difference measurement, particularly pulse signaltime-of-flight measurement and/or pulse signal time-of-flight differencemeasurement (dToF), wherein the system is also configured for carryingout a distance measurement on the basis of a phase measurement(phase-based distance measurement, PBR), particularly in cooperationwith a first object, wherein at least one first distance measurement tothe first object is carried out by means of phase measurement,particularly phase shift and/or change of a phase shift with thefrequency, and at least one signal time-of-flight measurement or asecond distance measurement is carried out on the basis of at least onesignal time-of-flight measurement to or via the first object,characterized in that the system for carrying out further signaltime-of-flight measurements, and/or distance measurements, and/orposition-finding, is calibrated using the at least one first phasemeasurement (PBR) on the basis of at least one signal time-of-flightmeasurement, particularly pulse signal time-of-flight measurement (ToF),and/or signal time-of-flight difference measurement, particularly pulsesignal time-of-flight difference measurement (dToF).

In one embodiment, for calibrating at least one system for carrying outa plurality of signal time-of-flight difference measurements, in eachcase between a shared first object and a second object of a plurality ofsecond objects, wherein the system is also configured for carrying outat least one first distance measurement, in particular between the firstobject and at least one reference object of the plurality of secondobjects, on the basis of a phase measurement, particularly incooperation of the first object with at least one of the plurality ofsecond objects, wherein the at least one first distance measurement tothe first object is carried out by means of phase measurement,particularly phase shift and/or change of a phase shift with thefrequency, and at least one plurality of signal time-of-flightdifference measurements between signal times-of-flight, in each casebetween the shared first object and a second object from the pluralityof second objects, also including the reference object, wherein that thesystem for carrying out further signal time-of-flight differencemeasurements between signal times-of-flight and/or distance measurementsand/or position-findings is calibrated by means of the at least onephase measurement, based on further signal time-of-flight differencemeasurements between signal times-of-flight, in each case between theshared first object and a second object from the plurality of secondobjects, and wherein the system, in particular, is configured forcarrying out a plurality of signal time-of-flight differencemeasurements between, in each case, the shared first object and a secondobject from a plurality of second objects, and to determine a distanceand/or position of the first object on the basis thereof. Especiallyadvantageously, the system is a “Time Difference of Arrival” system,particularly an Ultra Wide Band “Time Difference of Arrival” system(UWB-TDoA). The signals on which the time-of-flight measurements and/orthe phase measurements are performed are then, in particular, UWBsignals, particularly with a bandwidth of at least 500 MHz and/or of atleast 20% of the arithmetic mean of the upper and lower frequency limitsof the frequency band used.

The system preferably contains a second object and, in particular, thefirst object also. In particular, the distance- and/or time-of-flightmeasurements and/or time-of-flight difference measurements are carriedout between the first object and the at least one second object.

The problem is also solved by a use of at least one phase measurement onat least one signal between a first object and at least one secondobject, particularly at least one phase-based distance measurement(PBR), for calibrating at least one apparatus for signal time-of-flightmeasurement, particularly pulse signal time-of-flight (ToF), and/orsignal time-of-flight difference measurements, particularly pulse signaltime-of-flight difference measurement (dToF), and/or signaltime-of-flight-based, and/or signal time-of-flight differencemeasurement-based, distance measurement and/or position-finding of thefirst object and/or at least one second object.

Especially advantageously, the at least one apparatus is part of asystem for signal time-of-flight difference measurement-based distancemeasurement and/or position-finding of the first object, and/or thesystem comprises a plurality of second objects, in particular,stationary relative to one another, wherein the system is configured, inparticular, for carrying out a plurality of signal time-of-flightdifference measurements between, in each case, the shared first objectand a second object from a plurality of second objects, and to determineat least one distance and/or position of the first object on the basisthereof. Especially advantageously, the system is a “Time Difference ofArrival” system, particularly an Ultra Wide Band “Time Difference ofArrival” system (UWB-TdoA). The signals on which the time-of-flightmeasurements and/or the phase measurements are performed are then, inparticular, UWB signals, particularly with a bandwidth of at least 500MHz and/or of at least 20% of the arithmetic mean of the upper and lowerfrequency limits of the frequency band used.

The problem is also solved by an apparatus having a transmission andreceiving arrangement as well as a unit for phase measurement, anoscillator, a time measurer, the apparatus being configured for carryingout a signal time-of-flight measurement, having a control for carryingout the method by means of the apparatus.

The problem is also solved by a system comprising at least two objects,in particular, at least one first object and a plurality of secondobjects, having in each case a transmission and/or receivingarrangement, a PLL and/or oscillator, and in particular, a timemeasurer, and configured together for carrying out a signaltime-of-flight measurement between two of the objects and a phase-baseddistance measurement between two of the objects, said system having atleast one control for carrying out the method by means of the at leasttwo objects.

Particularly preferably, a plurality of second objects, particularlypositionally fixed relative to one another, is used. Particularly theplurality of second objects are configured for determiningtime-of-flight differences of a signal of the first object to theplurality of second objects, and therefrom, in particular, at least onepossible position of the first object [relative] to the second object.In particular, at least one of the second objects is a reference objectand is configured for carrying out at least one phase measurement and/ormeasurement of the change in phase shift on the basis of a frequencychange, and/or a phase-based distance measurement, on at least onesignal between the first object and reference object, in particular, ofthe first object, and the system is configured for calibrating thedetermination of the possible position, and/or for resolving itsambiguity, on the basis thereof. Especially advantageously, the systemis a “Time Difference of Arrival” system, particularly an Ultra WideBand “Time Difference of Arrival” system (UWB-TDoA). The signals onwhich the time-of-flight measurements and/or the phase measurements areperformed are then, in particular, UWB signals, particularly with abandwidth of at least 500 MHz and/or of at least 20% of the arithmeticmean of the upper and lower frequency limits of the frequency band used.

In particular, the system is formed by the first object, or the firstobject and at least one second object. In particular, the first and thesecond object are freely movable relative to one another, in particular,they are not mechanically connected. In particular, the first or secondobject is a key fob, and/or the other of the objects is a motor vehicleand/or a stationary object, and/or an object fixedly connected to anobject with an access prevention apparatus. In particular, thecalibration and/or the calibrated system is used for detecting a relayattack and/or for deciding on a release, for example, of a door and/or afunction, particularly ignition of a motor vehicle.

The signal time-of-flight measurement can be a signal round-trip timemeasurement, for example, from the second via the first to the second,or a measurement of the signal time-of-flight in one direction.

The phase-based distance measurement is particularly one based on thephase shift change caused by a frequency change, particularly on signalsbetween the second and first object.

The change in the phase shift caused by the frequency change,particularly between a first and a second frequency, is caused in that,particularly when both measurements are at approximately equal distance,a different number of wave packets fit within the distance, andconsequently the phase shift, which is caused by the distance, ends upbeing different between the frequencies. This change in the phase shiftas a result of the frequency is the phase change caused by the frequencychange. In this context, problems result during measuring since in eachcase, the phase measurement is dependent on a reference, and a,frequently undefined, phase jump can result when switching over totransmit the various frequencies. Switching over for transmitting and,particularly also for receiving, is thus preferably donephase-coherently, i.e., with a phase jump of zero. But determining orknowing the phase jump is also sufficient. Then one can determine thephase change by the frequency change, through the measured phase changecorrected by the phase jump upon switchover of the transmitter, and thephase jump upon switchover at the receiver, for measuring the measuredphase change.

For example, the distance can be [determined] by means of

Distance=(phase shift between two frequencies)/2/Pi/(difference betweenthe two frequencies)*c

where c is the speed of light

In particular, the change in phase shift is caused by the change offrequency at approximately the same distance. The phase shift is thuscaused by the distance. The change in the phase shift caused by thefrequency change or is caused in that, particularly when bothmeasurements are at approximately equal distance, a different number ofwave packets fit within the distance, and consequently the phase shift,which is caused by the distance, ends up being different between thefrequencies. This change in the phase shift as a result of the frequencyis the phase change caused by the frequency change. In this context,problems result during measuring since in each case, the phasemeasurement is dependent on a reference, and a frequently undefinedphase jump can result when switching over to transmit the variousfrequencies. Switching over for transmitting and, particularly also forreceiving, is thus preferably done phase-coherently, i.e., with a phasejump of zero. But determining or knowing the phase jump is alsosufficient. Then one can determine the phase change by the frequencychange, through the measured phase change corrected by the phase jumpupon switchover of the transmitter, and the phase jump upon switchoverat the receiver for measuring the measured phase change.

The information about switching time and/or phase jump is, inparticular, supplied, for example by predetermination or transmission.In principle, it is irrelevant where the calculations are carried out,whether in the objects, in one object, or in a central computing unit,for example. The measurements and information required for thecalculations to be carried out in each case are to be supplied there.

Thus, especially advantageously, the knowledge of the phase jump uponthe change in frequency is used to enable a simple measurement orcalculation, for example, for correcting the measurement of the changein phase shift. At a phase jump of zero, this knowledge is also used, inparticular, in that the measurement of the change in phase shift is useddirectly to calculate a distance, i.e., it is corrected only by zero.

Advantageously, a time synchronization between the first and secondobject and/or among multiple second objects is achieved and/or existsaccordingly with an accuracy greater than 2 ps, particularly in therange from 0.1 to 2 ps. The time synchronization lies particularly inthe range from 0.01 to 10 ns, particularly in the range from 0.05 to 5ns, and/or the drift of the timer is determined in the first and thirdobject and taken into account for the time-of-flight measurement, theaccuracy of the drift determination lies particularly in the range from0.01 to 100 ppb, particularly in the range from 1 to 10 ppb. This can beachieved by phase-coherent switching and evaluation thereof at thereceiver. For this purpose, the first and/or second object transmitsparticularly at least one signal at a first frequency and at a secondfrequency, and switches between them in a phase-coherent manner with aphase jump of zero, and/or such that the phase jump upon changing thefrequencies is known and/or determined upon transmitting. The timesynchronization, particularly between the multiple second objects, canalso be done on the basis of cable.

The phase difference or phase jump when switching between twofrequencies generally arises due to technical reasons, but can also beprevented. The switching between two frequencies can be carried out witha short interruption or interruption-free. At the time of theinterruption-free change, the phase jumps, or during the change withinterruption, the phase of the signals theoretically imagined tocontinue during the interruption, jumps before and after switching. Adefined phase jump exists at the change time-point without interruption,or at a theoretical change time-point during the interruption,particularly in the middle of the interruption and/or at the end of thesignal before the interruption or at the beginning of the signal afterthe interruption. This is the phase difference.

In particular, the distance measurement is also carried out by means ofa phase shift change caused by a frequency change. The second objecttransmits at least two different frequencies, particularly a first and asecond frequency, between which it switches in a phase-coherent manner,i.e., with a phase jump of zero, and/or switches such that the phasejump upon changing the frequencies is known and/or determined upontransmitting.

Thus, especially advantageously, the knowledge of the frequency jumpupon the change in frequency is used to enable a simple measurement orcalculation, for example, for correcting the measurement of the changein phase shift. At a phase jump of zero, this knowledge is also used, inparticular, in that the measurement of the change in phase shift is useddirectly to calculate a distance, i.e., it is corrected only by zero.

Preferably, the calibration is a calibration of the signaltime-of-flight measurement, particularly pulse time-of-flightmeasurement, and/or signal time-of-flight-based distance measurement,particularly pulse time-of-flight-based (ToF), between the first andsecond object. This makes sense, in particular, since a more accuratecalibration that relates to this pair can be achieved thereby. Inparticular, the method is carried out pair-wise, in each case for anobject with a plurality of other objects, and a calibration isundertaken for each pair, said calibration being used for measurementsbetween this pair for further signal time-of-flight measurements and/orsignal time-of-flight-based distance measurements.

Advantageously, the calibration is used for carrying out at least one,particularly a plurality of, signal time-of-flight measurement(s) and/orsignal time-of-flight-based distance measurement(s) of the system,particularly of the first object, in particular between the first andsecond object, particularly such that the calibration ascertains anoffset, particularly one that is dependent on frequency and/ortemperature, said offset being used as a correction in the at least onesignal time-of-flight measurement and/or signal time-of-flight-baseddistance measurement. A frequency- and/or temperature-dependent offset,and/or a frequency- or temperature-dependent calibration, increases theaccuracy. The offset can be composed, for example, of a plurality ofoffsets for, in each case, a frequency range, and/or temperature range,or through a function dependent on temperature and/or frequency.

Especially advantageously, the phase measurement and/or phase-baseddistance measurement is not and/or will not be calibrated in anapparatus-specific/system-specific, and/or merely model range-specificand/or series-specific, manner. This is particularly efficient.

Preferably, multiple phase measurements and/or phase-based distancemeasurements at different frequencies, and/or multiple measurements ofthe changes in the phase shifts with the frequency at differentfrequency spacings, are performed and/or used for the calibration, forreducing and/or excluding ambiguities, particularly with regard to theinaccuracy of the signal time-of-flight measurement and/or signaltime-of-flight-based distance measurement before the calibration. Thismakes it possible to also achieve a calibration with a large possibleoffset or a large fluctuation across model ranges and/or series.

Advantageously, the calibration is performed such that a difference,particularly a frequency- and/or temperature-dependent difference,between distance determined in a phase-based manner and signaltime-of-flight-based distance measurement is ascertained as a correctionterm, particularly frequency- and/or temperature-dependent, by means ofwhich one additional signal time-of-flight measurement and/or additionaldistance measurements are corrected on the basis of at least oneadditional signal time-of-flight measurement of the system, particularlyof the first object, particularly between the first and second object.This is a simple alternative and is usually sufficient to achieve anaccuracy of the calibration that makes sense in relation to thefluctuation of the time-of-flight measurement, particularly on the basisof time measurement inaccuracies.

Especially advantageously, the signal of the signal time-of-flightmeasurement and/or the signal on which the phase measurement isperformed, is a radio signal, in particular, a shared radio signal isused for signal time-of-flight measurement and at least one phasemeasurement. In this manner, for example, a signal at a first frequencycan be used for a phase measurement and signal time-of-flightmeasurement, and a second signal with a second frequency is used for anadditional phase measurement to measure the change in phase shift. Thesecond signal can also be used for an additional signal time-of-flightmeasurement, however. The signal time-of-flight measurements can then beaveraged, for example, and can be used with the phase-shift-change-basedmeasurement to determine the calibration or the offset or the correctionterm. This can be repeated at a plurality of first and secondfrequencies to improve the accuracy. However, it is also possible to usedifferent signals and/or frequencies for phase-based andtime-of-flight-based measurements. The frequencies, particularly thoseof measurements that are compared to one another, are similar to oneanother, in particular.

Especially advantageously, the signal time-of-flight is the signaltime-of-flight for a path between the second and first object, or thesignal round-trip time between the second and first object and back.

Preferably, the time spacing between the transmission of a signal forthe signal time-of-flight measurement and a signal for the phasemeasurement, particularly those to be compared to one another, is lessthan 500 ms. This increases the accuracy, particularly for changeabledistances and/or environments.

Especially advantageously, the calibration according to the invention isperformed individually in each case for a plurality of apparatusesand/or pairs of same-model apparatuses and/or apparatuses from a modelseries or series, wherein only a uniform calibration that is identicalfor all is used for the phase measurement and/or phase-based distancemeasurement for all apparatuses and/or pairs of the plurality. Thisincreases the accuracy with little effort, since the calibrations can beperformed rapidly and automatically, particularly at least when theobjects exchange signals among one another for the first time.

The problem is also solved by an apparatus having a transmission andreceiving arrangement as well as a unit for phase measurement, anoscillator, a time measurer, configured for carrying out a signaltime-of-flight measurement, having a control for carrying out the methodby means of the apparatus.

The problem is also solved by a system comprising two objects, having ineach case a transmission and/or receiving arrangement, and a unit forphase measurement, a PLL and/or oscillator, and in particular, a timemeasurer, and configured together for carrying out a signaltime-of-flight measurement between the two objects and a phase-baseddistance measurement between the two objects, said system having atleast one control for carrying out the method by means of the twoobjects.

Especially advantageously, the method is performed such that the phasemeasurements and/or signal time-of-flight measurements are performedwith signals in only one direction, particularly from the second to thefirst object. In particular, however, the method is also performed withreversed roles in the opposite direction.

Especially advantageously, the first and second object change betweenfirst and second frequencies phase-coherently and/or such that the phasejump is known and/or determined upon change of the frequencies duringtransmitting and/or upon receiving, and particularly the phases measuredupon reception are corrected by this phase jump or these phase jumps.This facilitates the calculation and enables particularly rapidexecution.

Especially advantageously, the method is carried out repeatedly with aplurality of pairs of first and second frequency. The accuracy can beincreased in this way, for example by averaging and/or reducing theambiguity.

In particular, the first and/or second object transmit a frequencyhopping by transmitting, in particular, approximately identicalfrequencies, wherein the sequence of these frequencies in the frequencyhopping of the first and second object is not decisive.

The frequencies are approximately identical or similar within themeaning of these statements particularly when they differ by less than5%, particularly less than 1% of the lower frequency, and/or less than17 MHz, particularly less than 10 MHz, particularly less than 9 MHz,particularly less than 2 MHz. For example, Object A can thus use thefrequencies FA1, FA2 to FAn, and Object B can use the frequencies FB1,FB2 to FBn, wherein 95% FAx<=FBx<=105% FAx, with x from 1 to n.

Frequency hopping particularly refers to consecutively transmitting ondifferent frequencies, of which pairs particularly always constitute afirst and a second frequency.

In particular, the frequencies, particularly of the frequencyhopping(s), lie in a spectrum from 25 to 100 MHz, in particular theycompletely span such a spectrum. Particularly the frequencies,particularly of the frequency hopping, lie in the range from 2 to 6 GHz.A spacing in the range from 0.1 to 17 MHz, particularly in the rangefrom 0.5 to 10 MHz lies particularly between adjacent but notnecessarily consecutive frequencies, particularly of the frequencyhopping, and/or between the first and second frequency.

Phase-coherent switching or changing between two frequencies isunderstood to mean, particularly, that the phase after the switching isknown relative to the phase situation before the switching. This is thecase when the change of phase when switching is zero, or is a previouslyknown or ascertainable value. In this manner, further measurements ofthe phase at the transmitter can be avoided, and the calculation can besimplified, particularly when frequencies are switched between withoutphase change. It is advantageous not only for the transmitting object toswitch in a phase-coherent manner, but also for the receiving object todo so, in particular a PLL is switched in a phase-coherent manner ineach object.

Alternatively, switching can be preferably phase-coherent, but also not,and the change in phase can be determined locally, i.e., particularly atthe transmitter before the transmission and/or at the receiver relativeto the PLL of the receiver, and this change can be corrected in thecalculation.

For example, when the point in time of the phase-coherent change or ofthe change with measured phase jump at the transmitting object is known,and when the change in the received signal is determined at the receivedobject, the time between transmitting and receiving the change isdetermined, which time represents the signal time-of-flight (ToF), andthe phase shift is also determined, which results solely from the signalflight. The distance can be directly determined from the signaltime-of-flight by means of the speed of light. This is also possible viathe phase shift, however with an ambiguity, which is generally moreaccurate. The ambiguity accompanying the phase-based measurement can bereduced by using multiple frequencies. A particularly accurate androbust distance measurement can be realized by combining the signaltime-of-flight measurements and phase-based measurements.

Phase-coherent switching between two frequencies is understood to mean,particularly, that the time-point of the switching is preciselydetermined and/or measured, and the phase after the switching, relativeto the phase position before the switching, is known. This is the casewhen the change of phase when switching is zero, or is equivalent to apreviously known value, or is measured at the transmitter.

Moreover, surprisingly, it was established that the distances obtainedfrom the one-sided distance measurement or the distance measurementaccording to the invention described here, are dependent upon thefrequency used for the distance determination when standard commercialtransceivers are used, such as the somewhat older cc2500 or the currentcc26xx by Texas Instruments or the Kw35/36/37/38 by NXP or the DA1469xby Dialog. In this context, inaccuracies in the transceivers also seemto result in calculated distances that are less than the actualdistance, but only with those frequencies whose transmission channel ishighly attenuated, such that these can be eliminated from thecalculation without issue.

Therefore, it is advantageous for the distance determination not to usesignal components of the object whose signals are used for the distancedetermination, for the distance determination in certain cases, andspecifically to not use such components that lie above an upper powerlimit and/or to not use such components that lie below a lower powerlimit. These limits can be predetermined, or can be determined based onthe received signals, and particularly can be above or below the meanreceived power, and can be particularly at least 20% above the meanreceived power (upper power limit) and/or at least 20% above the meanreceived power (lower power limit).

Preferably, not taken into account are signal components at frequenciesreceived with less than 40%, or at least signals received with less than20%, particularly less than 40%, of the mean energy of the signals,and/or signals received with greater than 140%, particularly withgreater than 120% of the mean energy.

Advantageously, the lower power limit lies in the range from 5 to 50% ofthe mean power of the received signals, and/or the upper lower limitlies in the range from 120 to 200% of the mean power of the receivedsignals.

In another embodiment, of the signals, particularly those selected inthe decision, the x % of the signals with the smallest receivedamplitude are sorted out and not used, and/or the y % of the signalswith the greatest received amplitude are sorted out and not used. It hasbeen shown to be particularly advantageous when the sum of x and y isnot less than 10 and/or does not exceed 75, and/or x lies in the rangefrom 10 to 75, and/or y lies in the range from 20 to 50. In mostsituations, high accuracy and reliable distance determination can beobtained with these values.

Preferably the first and/or second, or each of the two objects, sendsthe signals on multiple frequencies successively and/or consecutively,in particular directly consecutively. In particular, when sending istaking place by the first and second object, all signals of the first orof the second object are sent first, then those of the other. If one isworking with multiple objects, in particular they all send a frequencyhopping successively, particularly one frequency hopping each.Influences of environmental or distance changes, and of movements of oneor both objects, can be thus reduced.

Advantageously, at no time does the bandwidth of the signals exceed 50MHz, particularly 25 MHz. Consequently energy can be saved, interferencewith other processes can be prevented, and simple components can be usedcompared to broadband methods.

Preferably, a time- and/or clock-cycle synchronization and/or correctionis carried out between the two objects before, after and/or while themethod is carried out. This augments the accuracy of the method.Preferably, a drift of the clock of the first and/or second object, or adifference in the drift of the clock of the first and of the secondobject, is also determined and considered in the distance determinationor time-of-flight measurement. This augments the accuracy of the method.

The drift of the oscillators can be corrected for the phase measurementas known in the prior art and further improves the accuracy.

Advantageously, the method is carried out such that the frequencyspacing between two consecutive frequencies of the multiple frequenciesis at least 0.1 MHz and/or a maximum of 17 MHz, in particular is 10 MHz,and/or the multiple frequencies are at least five frequencies and/or amaximum of 200 frequencies, and/or wherein the multiple frequencies spana frequency band of at least two MHz and/or a maximum of 100 MHz. Thuscan a balanced measure be found between bandwidth requirement, whichimposes requirements for available frequencies and hardware, andaccuracy.

Advantageously, the objects are parts of a data transmission system,particularly a Bluetooth, WLAN, or radio data transmission system.Preferably, the signals are signals of the data transmission system,particularly of a data transmission standard, for example a radiostandard, WLAN or Bluetooth, which signals are used for datatransmission according to the data transmission standard.

Advantageously, the signals are transmitted over multiple antenna paths,particularly at least three, particularly with multiple antennas,particularly successively, sent at the sending object and/or received atthe receiving object with multiple antennas.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic depiction of the amplitude over the absolutetime.

FIG. 2 shows a schematic depiction of the change in phase shift due to afrequency change.

FIG. 3 shows a schematic depiction of the influence of the phase jumpwhen switching.

DETAILED DESCRIPTION

At the top, FIG. 1 shows a depiction of the amplitude over the absolutetime, purely schematically and not limiting. On the left can be seen asignal at the transmitter, the second object, in the form of theamplitude modulation, highly simplified here between zero and a value.Farther to the right, i.e., later in time, the received signal is shownat the receiver, the first object. The signal time-of-flight isillustrated by an arrow.

At the bottom, FIG. 1 shows a depiction of the amplitude over theabsolute time, purely schematically and not limiting. A signal withfrequency modulation is shown that can also be used for signaltime-of-flight measurement.

FIG. 2 shows, purely as an example and schematically, an illustration ofthe change in phase shift due to a frequency change. In the upperdepiction, a wave at a lower frequency (above) and a wave at a lowerfrequency (therebelow) is shown between two objects, respectively markedby a vertical line with a spacing marked by a double-ended arrow. It isevident that the phase change from the transmitter to the receiver endsup being different at the frequencies. In the lower image, the lowerwave is shown phase-shifted in order to also emphasize the change in thereceived phase based on the transmitted phase.

Purely schematically, FIG. 3 emphasizes the influence of the phase jumpwhen switching. In FIG. 3 , an object is respectively shown on the rightand left as vertical lines and between them, their spacing isillustrated by a double-ended arrow. A phase-coherent frequency switchis illustrated above in FIG. 3 , and a switch with phase jump isillustrated below in FIG. 3 . It is evident that the phase jump has aneffect on the change in phase difference between the phase at the firstand at the second object when switching frequencies. This can bemathematically corrected, however, if the phase jump is known.

1. A method for calibrating at least one system for carrying out one orboth of a signal time-of-flight measurement and a signal time-of-flightdifference measurement, wherein the system is configured in cooperationwith a first object, to carry out a distance measurement on the basis ofa phase measurement, wherein at least one first distance measurement tothe first object is carried out by means of the phase measurement, andat least one signal time-of-flight measurement or a second distancemeasurement is carried out on the basis of at least one signaltime-of-flight measurement to or via the first object, wherein thesystem for carrying out further signal time-of-flight measurements ordistance measurements or position-finding is calibrated by means of theat least one first phase measurement on the basis of at least one signaltime-of-flight measurement, or signal time-of-flight differencemeasurement.
 2. The method according to claim 1, wherein the systemcontains at least one second object and the distance or time-of-flightmeasurements are made between the first object and the at least onesecond object, or the performance of additional signal time-of-flightmeasurements or distance measurements or position-finding is calibratedby means of the at least one first phase measurement on the basis of atleast one signal time-of-flight measurement or signal time-of-flightdifference measurement.
 3. The method according to claim 1 forcalibrating at least one system for carrying out a plurality of signaltime-of-flight difference measurements, in each case between a sharedfirst object and a second object of a plurality of second objects,wherein the system is configured for carrying out the at least one firstdistance measurement between the first object and at least one referenceobject of the plurality of second objects, on the basis of the phasemeasurement, wherein the at least one first distance measurement to thefirst object is carried out by means of the phase measurement, and atleast one plurality of signal time-of-flight difference measurementsbetween signal times-of-flight, in each case between the shared firstobject and the second object from the plurality of second objects, alsoincluding the reference object, wherein the system for carrying outfurther signal time-of-flight difference measurements between signaltimes-of-flight or distance measurements or position-findings iscalibrated by means of the at least one phase measurement, based onfurther signal time-of-flight difference measurements between signaltimes-of-flight, in each case between the shared first object and thesecond object from the plurality of second objects.
 4. A use of at leastone phase measurement on at least one signal between a first object andat least one second object for calibrating at least one apparatus orsystem for signal time-of-flight measurement or signal time-of-flightdifference measurements or signal time-of-flight-based- or signaltime-of-flight-difference-based distance measurement or position-findingof the first object or of at least one second object.
 5. The useaccording to claim 4, wherein the at least one apparatus is part of asystem for signal time-of-flight difference measurement-based distancemeasurement or position-finding of the first object and comprises aplurality of second objects, wherein the system is configured forcarrying out a plurality of signal time-of-flight differencemeasurements between, in each case, the shared first object and a secondobject from the plurality of second objects, and to determine at leastone distance or position of the first object on the basis thereof. 6.The method according to claim 1, wherein the calibration is acalibration of one or both of the signal time-of-flight measurement andsignal time-of-flight-based distance measurement between the firstobject and the second object.
 7. The method according to claim 1,wherein the calibration is used for carrying out a plurality of signaltime-of-flight measurement(s) or signal time-of-flight-based distancemeasurement(s), distance measurements or position-findings, of thesystem, such that the calibration ascertains an offset that is dependenton frequency or temperature, said offset being used as a correction inthe at least one signal time-of-flight measurement or signaltime-of-flight-based distance measurement.
 8. The method according toclaim 1, wherein the phase measurement or phase-based distancemeasurement is not apparatus-specific/system-specific, or is or will becalibrated model range-specifically or series-specifically.
 9. Themethod according to claim 1, wherein multiple phase measurements orphase-based distance measurements at difference frequencies, or multiplemeasurements of changes in the phase shifts with the frequency atdifferent frequency spacings, are performed before the calibration andused for the calibration, for reducing or excluding ambiguities.
 10. Themethod according to claim 1, wherein a frequency- ortemperature-dependent difference, between distance determined in aphase-based manner and signal time-of-flight-based distance measurementis ascertained as a frequency-dependent or temperature-dependent,respectively, correction term by means of which one additional signaltime-of-flight measurement or additional distance measurements arecorrected on the basis of at least one additional signal time-of-flightmeasurement of the system.
 11. The method according to claim 1, whereinthe at least one signal of the signal time-of-flight measurement or thesignal on which the phase measurement is performed is a radio signalwhich contains a shared radio signal, and wherein the signaltime-of-flight is the signal time-of-flight for a path between thesecond object and the first object, or is the signal round-triptime-of-flight between the second object and the first object and back.12. The method according to claim 1, wherein time spacing between thetransmission of the at least one signal for the signal time-of-flightmeasurement and the at least one signal for the phase measurement isless than 500 ms or wherein the signal time-of-flight measurement and atleast one phase measurement are performed on same signal or on signalswith similar frequency.
 13. The method according to claim 1, isperformed individually in each case for a plurality of apparatuses orpairs of same-model apparatuses or apparatuses from a model range orseries, wherein only a uniform calibration that is identical for all isused for the phase measurement or phase-based distance measurement forall apparatuses or pairs of the plurality, respectively.
 14. Anapparatus having a transmission and receiving arrangement as well as aunit for phase measurement, an oscillator, a time measurer, configuredfor carrying out a signal time-of-flight measurement, having a controlfor carrying out the method according to claim 1 by means of theapparatus.
 15. A system comprising at least two objects, having in eachcase a transmission or receiving arrangement or both, a PLL oroscillator or both, and a time measurer, and configured together forcarrying out a signal time-of-flight measurement between the two objectsand a phase-based distance measurement between the two objects, havingat least one control for carrying out the method according to claim 1 bymeans of the at least two objects.
 16. The method according to claim 1,wherein the at least one first distance measurement to the first objectis carried out by means of phase measurement by means of one or both ofa phase shift and a change of a phase shift with the frequency.
 17. Themethod according to claim 3, wherein the system is configured forcarrying out a plurality of time-of-flight difference measurementsbetween, in each case, the shared first object and a second object froma plurality of second objects, and to determine a distance or positionof the first object on the basis thereof.
 18. The method according toclaim 1, wherein the calibration of the correction term isfrequency-dependent or temperature-dependent, or frequency andtemperature dependent.